All 11A57s launched after 1965 were functionally an 11A511 without the Soyuz's payload shroud and launch escape system. Around 300 were flown from Baikonur and Plesetsk through 1976 (various payloads, but Zenith PHOTINT satellites were the most common). The newer 11A511U core had been introduced in 1973, but the existing stock of 11A57s took another three years to use up.